Power receiving unit, power receiving control method, non-contact feed system, and electronic apparatus

ABSTRACT

A power receiving unit includes: a power receiving section configured to receive power that is fed from a power feeding unit in a non-contact manner; a rectification section configured to rectify the power received by the power receiving section; a method determination section configured to identify a feeding method of the power feeding unit; and a target voltage setting section configured to set a target voltage of the power rectified by the rectification section, to a value corresponding to the feeding method identified by the method determination section.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a Continuation of application Ser. No.14/526,629, filed Oct. 29, 2014, and claims the benefit of JapanesePriority Patent Application JP 2013-252798 filed Dec. 6, 2013, theentire contents of which are incorporated herein by reference.

BACKGROUND

The present disclosure relates to a power receiving unit receiving powerfrom a power feeding unit wirelessly (in a non-contact manner), a powerreceiving control method used in such a power receiving unit, and anon-contact feed system and an electronic apparatus that each use such apower receiving unit.

In recent years, a feed system performing wireless power feeding (alsocalled wireless power transfer, contact free, or non-contact powerfeeding) on consumer electronics devices (CE devices) such as mobilephones and portable music players has attracted attention. In such afeed system, for example, an electronic apparatus (such as a mobilephone) having a power receiving unit may be charged when the electronicapparatus is placed on a power feeding unit such as a power feedingtray. In other words, in such a feed system, the power feeding isallowed to be performed without connecting the power feeding unit andthe power receiving unit by a cable or the like.

Examples of the method of performing such wireless power feeding mayinclude, for example, an electromagnetic induction method and a magneticfield resonance method (also called magnetic resonance method) usingresonance phenomenon. In these methods, power is transmitted with use ofmagnetic coupling between a power feeding coil of a power feeding unitand a power receiving coil of a power receiving unit. Among them, ascompared with the electromagnetic induction method, advantageously, themagnetic field resonance method is allowed to transmit power even if thepower feeding unit and the power receiving unit are away from eachother, and feeding efficiency in the magnetic field resonance methoddoes not particularly drop even if positioning between the power feedingunit and the power receiving unit is insufficient.

SUMMARY

In recent years, the above-described feed system is actively studied,and commercialization thereof is progressing rapidly. Standardizationalso become active in association therewith, and wireless powerconsortium (WPC), power matters alliance (PMA), alliance for wirelesspower (A4WP), and the like actively perform creation of standards. Suchstandards organizations are different in feeding frequency and controlmethod from one another, and do not have compatibility basically. Inother words, there is a plurality of feeding methods. However, therespective technologies are extremely close to one another, and thus thepossibility that the compatibility is studied in the respectivestandards organizations in the future is adequately considered,similarly to near field communication (NFC).

Difference in feeding frequency is a large issue in compatibilitybetween the plurality of feeding methods. Difference in feedingfrequency indicates that L value of a power receiving coil necessary ona power receiving side is also different. In other words, in order toachieve compatibility between wireless feeding methods that aredifferent in feeding frequency from one another, it is necessary toidentify the feeding method by any way, and to change over the L valueitself according to the control of the feeding method. However, since alarge current flows in wireless feeding, a coil is frequently formed ofnot a substrate but a winding wire, and changing over of the L value byan intermediate tap or the like imposes a large load in terms of costand safety. Therefore, development of a system that is capable ofhandling the plurality of feeding methods without changing over the Lvalue of the power receiving coil or the like is desired.

In International Publication No. WO2010/035321, a feed system in which atarget voltage value on a power receiving side is set based on magnitudeof received power is disclosed. However, the feed system handles only aspecific feeding method, and does not handle a plurality of feedingmethods different in feeding frequency from one another.

It is desirable to provide a power receiving unit, a power receivingcontrol method, a non-contact feed system, and an electronic apparatusthat are capable of supplying power by a plurality of feeding methodssafely and efficiently.

According to an embodiment of the disclosure, there is provided a powerreceiving unit including: a power receiving section configured toreceive power that is fed from a power feeding unit in a non-contactmanner; a rectification section configured to rectify the power receivedby the power receiving section; a method determination sectionconfigured to identify a feeding method of the power feeding unit; and atarget voltage setting section configured to set a target voltage of thepower rectified by the rectification section, to a value correspondingto the feeding method identified by the method determination section.

According to an embodiment of the disclosure, there is provided a powerreceiving control method including: receiving power that is fed from apower feeding unit in a non-contact manner; rectifying the receivedpower; identifying a feeding method of the power feeding unit by amethod determination section; and setting, by a target voltage settingsection, a target voltage of the rectified power to a valuecorresponding to the feeding method identified by the methoddetermination section.

According to an embodiment of the disclosure, there is provided anon-contact feed system provided with a power feeding unit and a powerreceiving unit. The power receiving unit includes: a power receivingsection configured to receive power that is fed from the power feedingunit in a non-contact manner; a rectification section configured torectify the power received by the power receiving section; a methoddetermination section configured to identify a feeding method of thepower feeding unit; and a target voltage setting section configured toset a target voltage of the power rectified by the rectificationsection, to a value corresponding to the feeding method identified bythe method determination section.

According to an embodiment of the disclosure, there is provided anelectronic apparatus provided with a power receiving unit and a loadconnected to the power receiving unit. The power receiving unitincludes: a power receiving section configured to receive power that isfed from a power feeding unit in a non-contact manner; a rectificationsection configured to rectify the power received by the power receivingsection; a method determination section configured to identify a feedingmethod of the power feeding unit; and a target voltage setting sectionconfigured to set a target voltage of the power rectified by therectification section, to a value corresponding to the feeding methodidentified by the method determination section.

In the power receiving unit, the power receiving control method, thenon-contact feed system, and the electronic apparatus according to therespective embodiments of the disclosure, the feeding method of thepower feeding unit is identified, and the target voltage of therectified power is set to a value corresponding to the identifiedfeeding method.

According to the power receiving unit, the power receiving controlmethod, the non-contact feed system, and the electronic apparatusaccording to the respective embodiments of the disclosure, the feedingmethod of the power feeding unit is identified, and the target voltageof the rectified power on the power receiving side is set to the valuecorresponding to the identified feeding method. Therefore, it ispossible to supply power by the plurality of feeding methods safely andefficiently.

Note that effects of the embodiments of the present disclosure are notlimited to this effect, and may include any of effects that will bedescribed in the present disclosure.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary, and are intended toprovide further explanation of the technology as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the disclosure, and are incorporated in and constitutea part of this specification. The drawings illustrate embodiments and,together with the specification, serve to explain the principles of thetechnology.

FIG. 1 is an appearance perspective view illustrating an example of afeed system according to a first embodiment of the disclosure.

FIG. 2 is a block diagram illustrating an example of a circuitconfiguration of a feed system illustrated in FIG. 1.

FIG. 3 is a circuit configuration illustrating an example of anequivalent circuit of a feeding transmission system of a typicalnon-contact feed system.

FIG. 4 is a flowchart illustrating an example of a process ofcontrolling a target voltage on a power receiving unit side according toa feeding method in the feed system illustrated in FIG. 1.

FIG. 5 is a characteristic diagram illustrating an example ofrelationship between a feeding frequency and a rectified voltage in acase where a feeding method is a first method (method A) in the feedsystem illustrated in FIG. 1.

FIG. 6 is an explanatory diagram illustrating voltage variation by loadresistance in the first feeding method.

FIG. 7 is a characteristic diagram illustrating an example ofrelationship between a feeding frequency and a rectified voltage in acase where the feeding method is a second method (method B) in the feedsystem illustrated in FIG. 1.

FIG. 8 is a block diagram illustrating a first configuration example ofa regulator in a feed system according to a second embodiment.

FIG. 9 is a block diagram illustrating a first operation state of theregulator according to the first configuration example illustrated inFIG. 8.

FIG. 10 is a block diagram illustrating a second operation state of theregulator according to the first configuration example illustrated inFIG. 8.

FIG. 11 is a block diagram illustrating a second configuration exampleof the regulator.

FIG. 12 is a circuit diagram illustrating a third configuration exampleof the regulator.

FIG. 13 is a block diagram illustrating an example of a circuitconfiguration of a feed system according to a third embodiment.

FIG. 14 is a circuit diagram illustrating a configuration example of anovervoltage protection circuit in the feed system illustrated in FIG.13.

FIG. 15 is a circuit diagram illustrating a first configuration exampleof an overvoltage protection circuit or a communication section in afeed system according to a fourth embodiment.

FIG. 16 is a circuit diagram illustrating a second configuration exampleof the overvoltage protection circuit or the communication section inthe feed system according to the fourth embodiment.

DETAILED DESCRIPTION

Hereinafter, some embodiments of the disclosure will be described indetail with reference to drawings. Note that description will be givenin the following order.

-   1. First embodiment (an example of controlling a target voltage    according to a feeding method)

1.1 Configuration

1.2 Operation

1.3 Effects

-   2. Second embodiment (an example of changing over a method of    conversion operation of a regulator according to a feeding method)

2.1 First configuration example of regulator 210

2.2 Second configuration example of regulator 210

2.3 Third configuration example of regulator 210

2.4 Effects

-   3. Third embodiment (an example of controlling a protection setting    voltage according to a feeding method)

3.1 Configuration

3.2 Effects

-   4. Fourth embodiment (an example of changing over a circuit    configuration (a circuit constant) according to a feeding method)

4.1 Configuration example in which overvoltage protection circuit 214 ischanged over

4.2 Configuration example in which communication section 206 is changedover

4.3 Effects

-   5. Other embodiments

1. First Embodiment

[1.1 Configuration]

(Overall Configuration of Feed System 4)

FIG. 1 illustrates an overall configuration example of a feed system 4according to a first embodiment of the disclosure. FIG. 2 illustrates anexample of a circuit configuration of the feed system 4. Note that apower receiving unit, a power receiving control method, and anelectronic apparatus according to the respective embodiments of thedisclosure are embedded by the present embodiment, and therefore aredescribed together.

The feed system 4 is a system (a non-contact feed system) performingnon-contact power transmission (power supply, power feeding, or powertransmission) with use of a magnetic field (with use of magnetic fieldresonance, electromagnetic induction, or the like; the same applieshereinafter). The feed system 4 includes a power feeding unit 1 (aprimary-side unit) and one or a plurality of electronic apparatuses (inthis example, one electronic apparatus 2; a secondary-side unit) as afeeding target apparatus having a power receiving unit 3 (FIG. 2).

For example, as illustrated in FIG. 1, in the feed system 4, when theelectronic apparatus 2 is disposed on (or placed in the vicinity of) apower feeding surface (a power transmission surface) S1 of the powerfeeding unit 1, power transmission is performed from the power feedingunit 1 to the electronic apparatus 2. Here, as an example, the powerfeeding unit 1 has a mat shape (a tray shape) in which an area of thepower feeding surface S1 is larger than the electronic apparatus 2 to befed with power.

A power feeding coil 106 (FIG. 2) described later is disposed on thepower feeding surface S1 (on a side in contact with the power receivingunit 3 included in the electronic apparatus 2) of the power feeding unit1, and a power receiving coil 201 (FIG. 2) described later is disposedon a power receiving surface (on a side in contact with the powerfeeding unit 1) of the electronic apparatus 2. The power feeding unit 1transmits power to the electronic apparatus 2 with use of magneticcoupling through the power feeding coil 106 and the power receiving coil201. At this time, the power receiving unit 3 of the electronicapparatus 2 may communicates with the power feeding unit 1 through, forexample, load modulation, and instructs the power feeding unit 1 toincrease or decrease the feed power. As a result, a user is allowed tocharge the electronic apparatus 2 or the like without connecting analternating current (AC) adapter or the like with the electronicapparatus 2, which makes it possible to enhance usability of the user.

In the example of FIG. 1, the electronic apparatus 2 is a digitalcamera; however, the electronic apparatus 2 is not limited thereto. Forexample, various portable terminal devices such as a video camera, asmartphone, a mobile battery, a personal computer, a tablet, a phablet,an electronic book reader, an audio player, an audio recorder, aspeaker, a headphone, a head-mounted display, an accessory, a gamemachine, a wearable appliance, a glasses-type device, a wrist-mounteddevice, and a medical instrument may be used. The area of the powerfeeding surface S1 of the power feeding unit 1 may desirably larger thanan area of a power receiving surface of the electronic apparatus 2. Notethat this is not limitative, and for example, the area of the powerfeeding surface S1 may be equivalent to the area of the power receivingsurface of the electronic apparatus 2, or may be smaller than the areaof the power receiving surface of the electronic apparatus 2.

Moreover, the power feeding unit 1 may be configured so as to beembedded in other electronic apparatuses or electric appliances, or maybe configured so as to be embedded in a wall, a floor, or the like.Moreover, the electronic apparatus 2 may be configured so as to have afunction similar to that of the power feeding unit 1 in addition to thepower receiving unit 3, and to supply power to the other power receivingunits.

(Configuration of Power Feeding Unit 1)

As illustrated in FIG. 2, the power feeding unit 1 includes an AC/DCconverter 102, a power transmission driver 103, a control section 104, apower feeding section 10 having a capacitor 105 and the power feedingcoil 106, and a communication section 107.

The AC/DC converter 102 converts an AC power source 101 such as AC 100 Vinto DC low-voltage power, and supplies the DC low-voltage power to thepower transmission driver 103. Note that using the AC power 101 is anexample, and for example, a DC power source may be used as an inputpower source. The power feeding section 10 is connected to the powertransmission driver 103, and feed power of a predetermined feedingfrequency is supplied from the power transmission driver 103 to thepower feeding coil 106.

The power feeding coil 106 and the capacitor 105 are electricallyconnected in series to each other. The power feeding section 10 has afunction of using the power feeding coil 106 to radiate a magnetic field(magnetic flux) from the power feeding surface S1 toward the electronicapparatus 2. In the power feeding section 10, an LC resonance circuit isconfigured using the power feeding coil 106 and the capacitor 105.Further, the LC resonance circuit formed in the power feeding sectionand an LC resonance circuit formed in a power receiving section 20described later are magnetically coupled with each other (mutualinduction).

The communication section 107 bi-directionally communicates with thepower receiving unit 3. The communication by the communication section107 may be performed, for example, in such a manner that a transmissionsignal is superimposed on the feed power supplied from the powertransmission driver 103 to the power feeding coil 106. Specifically,information is modulated through amplitude shift keying (ASK), frequencyshift keying (FSK) or the like with use of a frequency of the feed powersupplied to the power feeding coil 106, as a carrier wave, and is thentransmitted. The transmission of the information from the powerreceiving unit 3 side to the communication section 107 is also performedby the similar method. Alternatively, the information may be transmittedfrom the power receiving unit 3 side to the communication section 107with use of a subcarrier whose frequency is different from that of thefeed power. As the method of bi-directionally transmitting informationtogether with power in a non-contact manner between adjacent coils,various methods are already used practically in communication between anon-contact IC card and a reader, or the like, and any method may beapplied in the example of the present disclosure.

Moreover, the communication section 107 may communicate with acommunication section 206 of the power receiving unit 3 described laterwith use of other wireless transmission paths different from the feedsystem or a wired transmission path without being limited to thecommunication method in which the transmission signal is superimposed onthe feed power to perform communication.

The communication section 107 may have a function of demodulating afeeding control signal that has been transmitted by the power receivingunit 3 of the electronic apparatus 2 through so-called load modulationwhile the power feeding unit 1 feeds power to the electronic apparatus2. The feeding control signal may contain information necessary for thefeeding operation, such as an increase request, a decrease request, orthe like of the feed power from the power receiving unit 3 to the powerfeeding unit 1.

The control section 104 controls the feed power supplied from the powertransmission driver 103 to the power feeding coil 106. The controlsection 104 may control the feeding operation of the power feeding unit1 based on the feeding control signal. At this time, the control section104 may control the power transmission driver 103 to change the feedingfrequency.

(Configuration of Electronic Apparatus 2 Having Power Receiving Unit 3)

As illustrated in FIG. 2, the electronic apparatus 2 includes the powerreceiving unit 3 and a load 204 that is connected to the power receivingunit 3. The power receiving unit 3 includes the power receiving section20, a rectification section 203, a control section 205, a communicationsection 206, a memory section 207, a frequency detection section 208, amethod determination section 209, a regulator 210, and a voltagemeasurement section 213. The power receiving section 20 includes thepower receiving coil 201, a capacitor 202A, and a capacitor 202B.

The power receiving section 20 receives power fed from the power feedingunit 1 in a non-contact manner. In the power receiving section 20, thepower receiving coil 201 and the capacitor 202A configure the LCresonance circuit. The power receiving coil 201 receives power from thepower feeding coil 106 of the power feeding unit 1. For example, basedon an electromagnetic field generated by the power feeding coil 106 ofthe power feeding unit 1, the power receiving section 20 may generate aninduced voltage according to change of the magnetic flux, in accordancewith law of electromagnetic induction.

The power receiving section 20 is connected to the rectification section203. The rectification section 203 rectifies power of a predeterminedfrequency received by the power receiving coil 201 to obtain DC power.The DC power obtained by the rectification section 203 is supplied tothe regulator 210.

The regulator 210 is a voltage converter converting the power rectifiedby the rectification section 203 into stable power of a predeterminedvoltage. The DC power of the predetermined voltage obtained by theregulator 210 is supplied to the load 204. Note that a secondary batterymay be charged instead of the load 204.

The communication section 206 bi-directionally communicates with thecommunication section 107 of the power feeding unit 1. To allow thecommunication section 206 to perform the communication, the seriescircuit of the power receiving coil 201 and the capacitor 202A isconnected to the communication section 206. The series circuit detectsthe signal superimposed on the power supplied from the power feedingunit 1 to receive the signal transmitted from the communication section107. Moreover, the signal transmitted from the communication section 206is supplied to the series circuit of the power receiving coil 201 andthe capacitor 202A.

The communication section 206 may have a function of transmitting thefeeding control signal that is supplied from the control section 205, tothe power feeding unit 1 through so-called load modulation while thepower feeding unit 1 feeds power to the electronic apparatus 2 (thepower receiving unit 3). Incidentally, as described above, the feedingcontrol signal may contain information necessary for the feedingoperation, such as the increase request, the decrease request, or thelike of the feed power to the power feeding unit 1. In addition, thecommunication with the power feeding unit 1 by the communication section206 is not limited to the load modulation, and various communicationmethods may be adopted similarly to the communication section 107 of thepower feeding unit 1 described above. Further, the communication section206 may have a function of receiving, from the power feeding unit 1, asignal including information that allows the feeding method to beidentified.

The frequency detection section 208 is connected to a transmission pathbetween the power receiving section 20 and the rectification section203, and detects the feeding frequency based on the power received bythe power receiving section 20. The method determination section 209identifies the feeding method of the power feeding unit 1. The methoddetermination section 209 is capable of identifying the feeding methodof the power feeding unit 1 based on the feeding frequency detected bythe frequency detection section 208. In the case where the communicationsection 206 receives a signal including information that allows thefeeding method to be identified from the power feeding unit 1, themethod determination section 209 is allowed to identify the feedingmethod of the power feeding unit 1 based on the signal received by thecommunication section 206.

The voltage measurement section 213 is connected to a transmission pathbetween the rectification section 203 and the regulator 210, and iscapable of measuring a voltage of the power rectified by therectification section 203.

The control section 205 sets the target voltage of the power rectifiedby the rectification section 203, to a value corresponding to thefeeding method identified by the method determination section 209.Further, the control section 205 outputs the feeding control signal thatinstructs the power feeding unit 1 to perform the feeding operation withthe power according to the target voltage, to the power feeding unit 1through the communication section 206.

In this way, in the first embodiment, the control section 205corresponds to a specific example of “target voltage setting section” inthe present disclosure.

The memory section 207 stores therein various kinds of controlinformation and the like used in the control section 205.

[1.2 Operation]

In the feed system 4 according to the first embodiment, as illustratedin FIG. 2, the power receiving unit 3 includes the frequency detectionsection 208 and the communication section 206, and the methoddetermination section 209 identifies the feeding method of the powerfeeding unit 1 based on the feeding frequency of the received power or acommunication result of the communication section 206. The controlsection 205 performs control to set the target voltage of the powerrectified by the rectification section 203, to a value corresponding tothe feeding method identified by the method determination section 209.

Here, prior to description of a specific example of the operation ofcontrolling the target voltage, the reason for changing the targetvoltage according to the feeding method is described.

FIG. 3 illustrates an example of an equivalent circuit of a feedingtransmission system of a typical non-contact feed system. In FIG. 3,like numerals are used to designate components substantially equivalentto those in the circuit illustrated in FIG. 2. A voltage V_(L) betweenboth ends of the load 204 on the power receiving side is represented bythe following expression (1) from FIG. 3. In a feeding system 100 ofFIG. 3, V_(in) indicates an AC voltage, Z_(in) indicates inputimpedance, I₁ indicates a current value, C₁ indicates a capacitancevalue, R₁′ indicates a resistance value, L₁′ indicates an L value of thepower feeding coil 106. In a receiving system 200 of FIG. 3, in the loadresistance (the load 204), a current value is denoted by I₂, the voltagevalue is denoted by V_(L), and the resistance value is denoted by R_(L).Moreover, in the power receiving system 200 of FIG. 3, C₂ indicates acapacitance value, R₂′ indicates a resistance value, and L₂′ indicatesan L value of the power receiving coil 201. k indicates a couplingcoefficient between the power feeding coil 106 and the power receivingcoil 201.

$\begin{matrix}{\left\lbrack {{Numerical}\mspace{14mu}{Expression}\mspace{14mu} 1} \right\rbrack\mspace{475mu}} & \; \\{{V_{L} = {{I_{2}R_{L}} = {\frac{\omega\;{MI}_{1}}{\sqrt{\left( {{\omega\; L_{2}^{\prime}} - \frac{1}{\omega\; C_{2}}} \right)^{2} + \left( {R_{2}^{\prime} + R_{L}} \right)^{2}}}R_{L}}}}{{{{where}\mspace{14mu}\omega} = {2\pi\; f}},{M = \sqrt{L_{1}^{\prime}L_{2}^{\prime}k}}}} & (1)\end{matrix}$

As is apparent from the expression (1), the voltage V_(L) on the powerreceiving side depends on various elements such as the L value L₁′ ofthe feeding system 100, the L value L₂′ of the receiving system 200, thecoupling coefficient k, and the feeding frequency f, in addition to theload resistance value R_(L). Since the parameters are largely varieddepending on the wireless feeding method, the voltage generated on thepower receiving side is inevitably varied.

Therefore, a way in which different methods are achieved with the same Lvalue by changing the target voltage without changing the L value itselfmay be considered. The target voltage on the power receiving sidelargely depends on the shape of the power receiving coil 201 and thehousing, and therefore, it is typically a matter of implementation. Asfor the target voltage, typically, a method in which a voltage is variedin response to the load current I₂, a method in which a set voltage isvaried between before the load connection and after the load connection,and the like may be used. Moreover, as for the target voltage value,some methods are disclosed in previous applications. For example, inInternational Publication No. WO2010/035321, the target voltage value isset based on the magnitude of the received power. Changing the targetvoltage value based on the received power is an important method interms of heat generation. However, in International Publication No.WO2010/035321, the wireless feeding is limited to a specific method,which does not handle methods different in feeding frequency.

In contrast, in the first embodiment, the target voltage is varied inorder to deal with a plurality of feeding methods. Next, a specificexample of operation of controlling the target voltage in the firstembodiment will be described.

(Operation Example of Controlling Target Voltage Based on FeedingMethod)

FIG. 4 illustrates an example of a control process of controlling thetarget voltage based on the feeding method. As illustrated in FIG. 4,when the power feeding from the power feeding unit 1 starts (at stepS11), an IC (circuits subsequent to the power receiving section 20) ofthe power receiving unit 3 is activated (at step S12). Typically, thefeed power at this time is minimum power necessary for activation of theIC. Upon activation of the circuits, the method determination section209 identifies the feeding method of the power feeding unit 1 (at stepS13). The identification of the feeding method may be performed based ona detection result of the feeding frequency by the frequency detectionsection 208 or the communication result of the communication section206.

When the feeding method is identified, the control section 205 sets thetarget voltage appropriate to the specification of the feeding method,and adjusts the voltage (at steps S14A and S15A, or at steps S14B andS15B). Specifically, the control section 205 outputs the feeding controlsignal that instructs the power feeding unit 1 to perform the feedingoperation with the power according to the target voltage, to the powerfeeding unit 1 through the communication section 206. Incidentally, inthe example of FIG. 4, a control example in which the first feedingmethod (the method A) and the second feeding method (the method B) areidentified and the target voltage is set to VA or VB is illustrated;however, three or more feeding methods may be identified, and the targetvoltage may be set to any of three or more values. When the voltagereaches the target voltage range (Y at step S16A or Y at step S16B), thecontrol section 205 ends the operation of controlling the targetvoltage.

When the voltage does not reach the target voltage range (N at the stepS16A or N at the step S16B), it is expected that the power feeding isnot performed with the appropriate voltage, and therefore, heatgeneration and interference caused by efficiency degradation mayadversely affect. Therefore, for example, the control section 205 mayperform a forced termination process of the power feeding (at a stepS17A and a step S17B).

By the above-described process, it is possible to adjust the targetvoltage appropriate to each of the feeding method, and to handle theplurality of feeding methods with use of the same power receiving coil201.

(Specific Setting Example of Target Voltage)

As the power control in the wireless power feeding, various controls bythe frequency, the voltage, the duty ratio, and the like of the powersignal are performed. Here, an example of controlling the power by thefeeding frequency will be described.

FIG. 5 illustrates an example of relationship between the feedingfrequency and the rectified voltage in the case of the first feedingmethod (the method A). It is found from FIG. 5 that the voltage controlrange is wide under the light load (at the time of initial activation)such as the load resistance of about 1 kΩ or about 100Ω. For example,when the load resistance is about 1 kΩ, it is possible to select adesired voltage within the voltage range of about 7 V to about 16 V.

However, typically, it is not preferable that the power feeding beperformed at the range where the voltage is largely varied inassociation with variation of the load, in terms of control. Typically,after the target voltage is set under the light load (only system load)as control, a heavy load such as a battery is connected. However, if thevoltage variation is large, the system may be disadvantageously stoppedor large power may not be disadvantageously used.

As an example, FIG. 6 illustrates voltage variation by the loadresistance in the method A. For example, it is assumed that theresistance value before the load (such as a buttery) connection is about1 kΩ and the resistance value after the connection is about 5Ω (forexample, about 5 V and about 1 A). It is found from FIG. 6 that thereare a frequency at which the voltage variation by the variation of theload resistance is large and a frequency at which the voltage variationis small. For example, when the voltage before the load connection (theload resistance value is about 1 kΩ) is adjusted to about 7 V and thenthe load is connected, the voltage drop is suppressed to about 1 V. Incontrast, when the voltage before the load connection is adjusted toabout 14 V and then the load is connected, the voltage is varied byabout 10 V or more. A major factor thereof is increase of the impedanceon the power feeding side. In other words, in the example of the methodA, it is found that the target voltage under the light load may bedesirably set to about 7 V in terms of control.

FIG. 7 illustrates an example of relationship between the feedingfrequency and the rectified voltage in the case of the second feedingmethod (the method B). The power receiving coil 201 used is the same asthat in the method A. The rectified voltage when the load resistance isabout 1 kΩ is about 11.5 V to about 15 V in the method B, and theadjustable range is narrower than that of the method A. In other words,when the target voltage is set to about 7 V for the light load that isappropriate in the method A, the voltage is adjustable to the targetvoltage in the method A; however, the voltage may not become the targetvoltage in the method B. Accordingly, it is understood that theappropriate target voltage may be varied depending on the method.

[1.3 Effects]

As described above, according to the first embodiment, the targetvoltage of the rectified power on the power receiving side is set to avalue corresponding to the identified feeding method. Therefore, it ispossible to perform the power feeding without changing over the powerreceiving coil 201 in each of the plurality of wireless feeding methods.Moreover, since the appropriate target voltage is set based on each ofthe feeding methods, it is possible to achieve the power feeding withhigh efficiency and high safety in each of the plurality of wirelessfeeding methods.

Note that the effects described in the present specification are merelyexamples without limitation, and other effects may be obtainable. Thesame applies to the following other embodiments and modifications.

2. Second Embodiment

(An Example of Changing Over a Method of Conversion Operation of aRegulator According to a Feeding Method)

In the second embodiment, the method of the conversion operation of theregulator 210 is changed over according to the feeding method. FIG. 8 toFIG. 12 each illustrate a configuration example of the regulator 210 inthe second embodiment. Note that, in the second embodiment, theconfigurations and operation other than parts relating to theconfiguration and the control operation of the regulator 210 may besubstantially similar to those in the above-described first embodiment(FIG. 1 to FIG. 2, and FIG. 4).

In the wireless power feeding, any of a low drop out (LDO) and a DC-DCconverter is frequently used as the regulator 210 that makes the voltageconstant. The LDO allows the voltage difference to be lost to generate aconstant voltage. For example, in the case where the input voltage isabout 5.2 V and the output voltage is about 5.0 V, when the current ofabout 1 A is received, the loss of about 0.2 W occurs by a potentialdifference of about 0.2 V and the current of about 1 A. If the inputvoltage is about 6.0 V, the loss of about 1 W occurs by the voltagedifference of about 1 V and the current of about 1 A. In other words,the LDO has characteristics that the LDO is driven at a low voltage,higher efficiency is obtained as a voltage difference is small, and asmall number of external components is necessary while fine adjustmentof the input voltage is necessary. On the other hand, the DC-DCconverter has disadvantages that a potential difference of a certainlevel or more is necessary and maximum efficiency is lower than that ofthe LDO while the DC-DC converter allows the voltage to be constant atcertain efficiency even if there is a potential difference by theswitching operation.

Therefore, in the second embodiment, the method of the conversionoperation of the regulator 210 is changed over according to the feedingmethod. As an example, a way in which the LDO is used in theabove-described method A because the voltage under the light load isdifficult to be generated, and the DC-DC converter is used in the methodB because the voltage under the light load is high.

In the second embodiment, the regulator 210 converts the power rectifiedby the rectification section 203 into power of the desired voltage, andhas a plurality of methods used for the conversion operation. Thecontrol section 205 changes over the method of the conversion operationperformed by the regulator 210, according to the feeding methodidentified by the method determination section 209.

In FIG. 8 to FIG. 12, cases where the regulator 210 includes two typesof conversion circuits, namely, a DC-DC converter 211 and an LDO 212 aredescribed below as configuration examples. The DC-DC converter 211 iscalled a switching regulator. The DC-DC converter 211 is a circuit thatswitches the input power source by a switching element at relativelyhigh speed, and rectifies and smoothes the switched power source to beDC power source of the desired voltage. The DC-DC converter 211 has awide variable range of the input voltage.

The LDO 212 is a series regulator that controls the voltage drop amountin a transistor, and regulates power to DC power of the desired voltage.When the variable range of the input voltage is narrow and the inputvoltage is slightly higher than the output voltage, the LDO 212 performsefficient voltage conversion.

The regulator 210 uses one circuit of the DC-DC converter 211 and theLDO 212 to convert the voltage into a stable constant voltage. Thecircuit used for the conversion operation by the regulator 210 isdetermined by instruction from the control section 205 that controlspower receiving.

[2.1 First Configuration Example of Regulator 210]

FIG. 8 illustrates a first configuration example of the regulator 210.In the first configuration example, the DC-DC converter 211 and the LDO212 are connected in series to each other. The LDO 212 is connected in arear stage of the DC-DC converter 211 in the example of FIG. 8; however,the connection order may be inverted. The DC-DC converter 211 and theLDO 212 are set so that only one thereof is actuated. Stopped one out ofthe DC-DC converter 211 and the LDO 212 outputs the input signal as itis.

FIG. 9 illustrates a first operation state of the regulator 210according to the first configuration example illustrated in FIG. 8. FIG.10 illustrates a second operation state of the regulator 210 accordingto the first configuration example illustrated in FIG. 8.

When the DC-DC converter 211 is used, as illustrated in FIG. 9, thecontrol section 205 actuates the DC-DC converter 211, and allows thevoltage to pass through the LDO 212. As a result, the voltage convertedby the DC-DC converter 211 is obtained at the output part of theregulator 210.

Moreover, when the LDO 212 is used, as illustrated in FIG. 10, thecontrol section 205 actuates the LDO 212, and allows the voltage to passthrough the DC-DC converter 211. As a result, the voltage converted bythe LDO 212 is obtained at the output part of the regulator 210.

[2.2 Second Configuration Example of Regulator 210]

FIG. 11 illustrates a second configuration example of the regulator 210.In the second configuration example, the DC-DC converter 211 and the LDO212 are connected in parallel to each other. The control section 205controls the actuation side so that any one of the DC-DC converter 211and the LDO 211 is actuated.

[2.3 Third Configuration Example of Regulator 210]

FIG. 12 illustrates a third configuration example of the regulator 210.In the third configuration example, the DC-DC converter 211 shares acircuit with the LDO 212. As illustrated in FIG. 12, two transistors Q1and Q2 are connected between an input terminal 210 a of the regulator210 and a ground potential part. The two transistors Q1 and Q2 arecontrolled to be turned on or off by the control section 205. Aconnection point between the transistors Q1 and Q2 is connected to anoutput terminal 210 b of the regulator 210 through a coil L11. An end ofa smoothing capacitor C11 is connected to a connection point between thecoil L11 and the output terminal 210 b.

A series circuit of resistors R11 and R12 for voltage detection isconnected between the ground potential part and the connection pointbetween the transistors Q1 and Q2 and the coil L11. Moreover, a seriescircuit of resistors R13 and R14 for voltage detection is connectedbetween the ground potential part and the connection point between thecoil L11 and the output terminal 210 b. The control section 205 detectsa voltage of a connection point between the resistors R11 and R12 and avoltage of a connection point between the resistors R13 and R14.

When the regulator 210 is used as the DC-DC converter 211 with theconfiguration illustrated in FIG. 12, the control section 205 turns onor off the two transistors Q1 and Q2 at a high speed, to performswitching operation. At this time, the control section 205 monitors thevoltage charged to the smoothing capacitor C11, from the voltage at theconnection point between the resistors R13 and R14, and controls theswitching state of each of the two transistors Q1 and Q2 so that thedetected voltage becomes appropriate.

Further, when the regulator 210 is used as the LDO 212 with theconfiguration illustrated in FIG. 12, the control section 205 controlsthe transistor Q1 to operate as a voltage control element. Thetransistor Q2 is set to an open state by the control section 205. Atthis time, the control section 205 detects the voltage at the connectionpoint between the resistors R11 and R12, and controls the voltage dropamount of the transistor Q1 so that the detected voltage becomesappropriate.

[2.4 Effects]

As described above, according to the second embodiment, the method ofthe conversion operation of the regulator 210 is changed over accordingto each of the plurality of wireless feeding methods. Therefore, it ispossible to achieve the power feeding with high efficiency and highsafety in each of the plurality of wireless feeding methods.

3. Third Embodiment

(An Example of Controlling a Protection Setting Voltage According to aFeeding Method)

[3.1 Configuration]

FIG. 13 illustrates an example of a circuit configuration of a feedsystem 4 according to a third embodiment. FIG. 14 illustrates aconfiguration example of an overvoltage protection circuit 214 in thefeed system 4 illustrated in FIG. 13. In the third embodiment, asillustrated in FIG. 13, the power receiving unit 3 includes theovervoltage protection circuit 214, and the control section 205 controlsan overvoltage protection (OVP) voltage in the overvoltage protectioncircuit 214 according to the feeding method. Incidentally, in the thirdembodiment, configurations and operation other than parts relating tothe configuration and the control operation of the overvoltageprotection circuit 214 may be substantially similar to those of theabove-described first embodiment (FIG. 1 to FIG. 2, and FIG. 4).Moreover, a configuration obtained by combining the third embodiment andthe above-described second embodiment (FIG. 8 to FIG. 12) may beavailable.

The overvoltage protection circuit 214 lowers the voltage of the powerreceived by the power receiving section 20 so that the voltage does notexceed the overvoltage protection voltage. The control section 205 setsthe protection voltage to a value corresponding to the feeding methodidentified by the method determination section 209.

As described above, in the third embodiment, the control section 205corresponds to a specific example of “protection voltage settingsection” in the present disclosure.

The overvoltage protection voltage is described now. The overvoltageprotection voltage is a voltage set to prevent the IC from beingdamaged, and the overvoltage protection circuit 214 operates when thevoltage exceeds the overvoltage protection voltage. Examples of theovervoltage protection circuit 214 may include a method of allowing alarge capacitor typically called a cramp circuit to be short-circuited,and a Zener diode.

As illustrated in FIG. 13, the overvoltage protection circuit 214 isdisposed on a transmission path between the power receiving section 20and the rectification section 203. As illustrated in FIG. 14, forexample, the overvoltage protection circuit 214 may include a capacitor301 and a capacitor 302. A first end of the capacitor 301 is connectedto a transmission path on a high voltage side of the power receivingunit 3, and a first end of the capacitor 302 is connected to atransmission path on a low voltage side of the power receiving unit 3.Moreover, MOSFETs 303 and 304 are provided between a second end of thecapacitor 301 and a second end of the capacitor 302. A gate of each ofthe MOSFETs 303 and 304 is connected to the control section 205. In theconfiguration example of FIG. 14, a circuit that allows the MOSFETs 303and 304 to be turned on to lower the voltage when the measured voltageexceeds the overvoltage protection voltage is configured.

The overvoltage protection is important for not only withstand voltageof the IC but also prevention of excessive lowering of efficiency. Forexample, in the case where the regulator 210 is the LDO, if acircumstance of generating about 30 V occurs, loss of 25 V×current valueoccurs when the output is regulated to about 5 V. Even if the currentvalue is about 100 mA, loss of about 2.5 W occurs. Specifically, in thecase where the LDO is operated at a constant voltage basically, theovervoltage protection voltage should not be excessively increased evenif the withstand voltage of the IC is sufficient. However, there is apossibility that operation may be performed or is inevitably performedat slightly higher voltage in other methods. For example, in the case ofthe third embodiment, the overvoltage protection voltage may bedesirably set to about 12 V in the above-described method A; however,there is a possibility that operation is not performed by the method Bin this setting. Therefore, it is necessary to appropriately change overthe overvoltage protection voltage.

[3.2 Effects]

As described above, according to the third embodiment, the protectionvoltage is appropriately set according to each of the plurality ofwireless feeding methods. Therefore, it is possible to achieve the powerfeeding with high efficiency and high safety in each of the plurality ofwireless feeding methods.

4. Fourth Embodiment

(An Example of Changing Over a Circuit Configuration (A CircuitConstant) According to a Feeding Method)

[4.1 Configuration Example in Which Overvoltage Protection Circuit 214is Changed Over]

In the present configuration example, the configurations and operationother than parts relating to the configuration and the control operationof the overvoltage protection circuit 214 may be substantially similarto those of the above-described first embodiment (FIG. 1 to FIG. 2, andFIG. 4). Moreover, in the present configuration example, the basicconfiguration of the entire feed system 4 including the overvoltageprotection circuit 214 may be substantially similar to that in FIG. 13.Further, a configuration obtained by combining the present configurationexample and the above-described second embodiment (FIG. 8 to FIG. 12)may be available.

In the above-described third embodiment (FIG. 14), the protectionvoltage is set to a voltage according to the feeding method, while thecircuit configuration (the circuit constant) itself of the overvoltageprotection circuit 214 is not changed. However, an appropriate circuitconstant may be varied according to the feeding method, in addition tothe protection voltage. Therefore, in the present configuration example,in addition to the protection voltage, the circuit configuration (thecircuit constant) of the overvoltage protection circuit 214 is changedover to an appropriate circuit configuration (an appropriate circuitconstant) according to the feeding method.

FIG. 15 illustrates a first configuration example of the overvoltageprotection circuit 214 according to the fourth embodiment. In the firstconfiguration example of FIG. 15, the overvoltage protection circuit 214has a plurality of overvoltage protection circuits 214A and 214B. Theovervoltage protection circuit 214A is configured of capacitors 301A and302A and MOSFETs 303A and 304A. A gate of each of the MOSFETs 303A and304A is connected to the control section 205. The overvoltage protectioncircuit 214B is configured of capacitors 301B and 302B and MOSFETs 303Band 304B. A gate of each of the MOSFETs 303B and 304B is connected tothe control section 205. The circuit configuration (the circuitconstant) of the overvoltage protection circuit 214A is a configurationsuitable for a case where the feeding method is the above-describedmethod A. Specifically, a capacitance value of each of the capacitors301A and 302A is X [nF]. Moreover, the circuit configuration (thecircuit constant) of the overvoltage protection circuit 214B is aconfiguration suitable for a case where the feeding method is theabove-described method B. Specifically, a capacitance value of each ofthe capacitors 301B and 302B is Y [nF] that is different from thecapacitance value of each of the capacitors 301A and 302A.

FIG. 16 illustrates a second configuration example of the overvoltageprotection circuit 214 according to the fourth embodiment. In the secondconfiguration example of FIG. 16, resistors 301Ar and 302Ar are used inthe overvoltage protection circuit 214A in place of the capacitors 301Aand 302A of the first configuration example of FIG. 15. Moreover,resistors 301Br and 302Br are used in the overvoltage protection circuit214B in place of the capacitors 301B and 302B. The circuit configuration(the circuit constant) of the overvoltage protection circuit 214A is aconfiguration suitable for a case where the feeding method is theabove-described method A. Specifically, a resistance value of each ofthe resistors 301Ar and 302Ar is X [Ω]. Moreover, the circuitconfiguration (the circuit constant) of the overvoltage protectioncircuit 214B is a configuration suitable for a case where the feedingmethod is the above-described method B. Specifically, a resistance valueof each of the resistors 301Br and 302Bt is Y [Ω] that is different fromthe resistance value of each of the resistors 301Ar and 302Ar.

In the configuration example illustrated in FIG. 15 or FIG. 16, thecontrol section 205 controls the overvoltage protection circuit 214 sothat any one of the plurality of overvoltage protection circuits 214Aand 214B is selectively used according to the feeding method identifiedby the method determination section 209. In the case where the feedingmethod is the above-described method A, the control section 205 turns onthe MOSFETs 303A and 304A of the overvoltage protection circuit 214A tolower the voltage when the measured voltage exceeds the overvoltageprotection voltage of the method A. In addition, in the case where thefeeding method is the above-described method B, the control section 205turns on the MOSFETs 303B and 304B to lower the voltage when themeasured voltage exceeds the overvoltage protection voltage of themethod B.

[4.2 Configuration Example in Which Communication Section 206 is ChangedOver]

In the above description, the configuration example in which the circuitconfiguration (the circuit constant) of the overvoltage protectioncircuit 214 is changed over has been illustrated. However, thecommunication section 206 may have a configuration similar to that ofthe overvoltage protection circuit 214 illustrated in FIG. 15 and FIG.16, and the circuit configuration (the circuit constant) of thecommunication section 206 may be changed over to an appropriate circuitconfiguration (an appropriate circuit constant) according to the feedingmethod.

For example, the communication section 206 may have a plurality ofcommunication circuits 206A and 206B as with the configuration exampleillustrated in FIG. 15 or FIG. 16. In the configuration exampleillustrated in FIG. 15 or FIG. 16, the control section 205 controls thecommunication section 206 so that any one of the plurality ofcommunication circuits 206A and 206B is selectively used according tothe feeding method identified by the method determination section 209.The control section 205 selectively turns on the MOSFETs 303A and 304Aor the MOSFETs 303B and 304B to change over the communication circuits206A and 206B according to the feeding method.

Note that the configurations and operation other than parts relating tothe configuration and the control operation of the communication section206 may be substantially similar to those in the above-described firstembodiment (FIG. 1 to FIG. 2, and FIG. 4). Moreover, a configurationobtained by combining the present configuration example and one of theabove-described second embodiment (FIG. 8 to FIG. 12) and theabove-described third embodiment (FIG. 13 and FIG. 14) may be available.Moreover, both of the overvoltage protection circuit 214 and thecommunication section 206 may have a plurality of circuit configurations(circuit constants) according to the feeding methods, and the controlsection 205 may change over the circuit configurations (the circuitconstants) of both to an appropriate circuit configuration (anappropriate circuit constant) according to the feeding method.

[4.3 Effects]

As described above, according to the fourth embodiment, one or both ofthe circuit configurations of the overvoltage protection circuit 214 andthe communication section 206 are changed over according to each of theplurality of wireless feeding methods. Therefore, it is possible toachieve power feeding with high efficiency and high safety in each ofthe plurality of wireless feeding methods.

5. Other Embodiments

The technology of the present disclosure is not limited to theabove-described embodiments, and various modifications may be made.

For example, the present technology may be configured as follows.

(1) A power receiving unit including:

a power receiving section configured to receive power that is fed from apower feeding unit in a non-contact manner;

a rectification section configured to rectify the power received by thepower receiving section;

a method determination section configured to identify a feeding methodof the power feeding unit; and

a target voltage setting section configured to set a target voltage ofthe power rectified by the rectification section, to a valuecorresponding to the feeding method identified by the methoddetermination section.

(2) The power receiving unit according to (1), further including:

a communication section configured to communicate with the power feedingunit; and

a control section configured to output a signal to the power feedingunit through the communication section, the signal instructing the powerfeeding unit to perform feeding operation with the power correspondingto the target voltage.

(3) The power receiving unit according to (1) or (2), further including

a frequency detection section configured to detect a feeding frequencybased on the power received by the power receiving section, wherein

the method determination section identifies the feeding method of thepower feeding unit based on the feeding frequency detected by thefrequency detection section.

(4) The power receiving unit according to (1) or (2), further including

a communication section configured to receive a signal from the powerfeeding unit, the signal containing information that allows the feedingmethod to be identified, wherein

the method determination section identifies the feeding method of thepower feeding unit based on the signal received by the communicationsection.

(5) The power receiving unit according to any one of (1) to (4), furtherincluding:

a regulator configured to convert the power rectified by therectification section into power of a desired voltage, the regulatorhaving a plurality of methods used in the conversion operation; and

a control section configured to change over the method of the conversionoperation performed by the regulator, according to the feeding methodidentified by the method determination section.

(6) The power receiving unit according to any one of (1) to (5), furtherincluding:

a protection circuit configured to lower a voltage of the power receivedby the power receiving section not to exceed a protection voltage; and

a protection voltage setting section configured to set the protectionvoltage to a value corresponding to the feeding method identified by themethod determination section.

(7) The power receiving unit according to any one of (1) to (5), furtherincluding:

a protection circuit section having a plurality of overvoltageprotection circuits different in circuit constant from one another; and

a control section configured to control the protection circuit sectionto selectively use any one of the plurality of overvoltage protectioncircuits according to the feeding method identified by the methoddetermination section.

(8) The power receiving unit according to any one of (1) to (7), furtherincluding:

a communication section having a plurality of communication circuitsdifferent in circuit constant from one another; and

a control section configured to control the communication section toselectively use any one of the plurality of communication circuitsaccording to the feeding method identified by the method determinationsection.

(9) A power receiving control method, including:

receiving power that is fed from a power feeding unit in a non-contactmanner;

rectifying the received power;

identifying a feeding method of the power feeding unit by a methoddetermination section; and

setting, by a target voltage setting section, a target voltage of therectified power to a value corresponding to the feeding methodidentified by the method determination section.

(10) A non-contact feed system provided with a power feeding unit and apower receiving unit, the power receiving unit including:

a power receiving section configured to receive power that is fed fromthe power feeding unit in a non-contact manner;

a rectification section configured to rectify the power received by thepower receiving section;

a method determination section configured to identify a feeding methodof the power feeding unit; and

a target voltage setting section configured to set a target voltage ofthe power rectified by the rectification section, to a valuecorresponding to the feeding method identified by the methoddetermination section.

(11) An electronic apparatus provided with a power receiving unit and aload connected to the power receiving unit, the power receiving unitincluding:

a power receiving section configured to receive power that is fed from apower feeding unit in a non-contact manner;

a rectification section configured to rectify the power received by thepower receiving section;

a method determination section configured to identify a feeding methodof the power feeding unit; and

a target voltage setting section configured to set a target voltage ofthe power rectified by the rectification section, to a valuecorresponding to the feeding method identified by the methoddetermination section.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations, and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

What is claimed is:
 1. A power receiving unit comprising: a powerreceiving section configured to receive power that is fed from a powerfeeding unit wirelessly; a determination circuit configured to identifya feeding method of the power feeding unit; and a control circuitconfigured to set a target voltage of the power to a value correspondingto the feeding method identified by the determination circuit.
 2. Thepower receiving unit according to claim 1, further comprising: arectification circuit configured to rectify the power received by thepower receiving section.
 3. The power receiving unit according to claim1, further comprising: a communication circuit configured to communicatewith the power feeding unit, wherein the control circuit is configuredto output a signal to the power feeding unit through the communicationcircuit, the signal instructing the power feeding unit to performfeeding operation with the power corresponding to the target voltage. 4.The power receiving unit according to claim 1, further comprising: afrequency detection circuit configured to detect a feeding frequencybased on the power received by the power receiving section, wherein thedetermination circuit identifies the feeding method of the power feedingunit based on the feeding frequency detected by the frequency detectioncircuit.
 5. The power receiving unit according to claim 1, furthercomprising: a communication circuit configured to receive a signal fromthe power feeding unit, the signal containing information that allowsthe feeding method to be identified, wherein the determination circuitidentifies the feeding method of the power feeding unit based on thesignal received by the communication circuit.
 6. The power receivingunit according to claim 1, further comprising: a regulator configured toconvert the power rectified by the rectification circuit into power of adesired voltage, the regulator having a plurality of methods used in theconversion operation, wherein the control circuit is configured tochange over the method of the conversion operation performed by theregulator, according to the feeding method identified by thedetermination circuit.
 7. The power receiving unit according to claim 1,further comprising: a protection circuit configured to lower a voltageof the power received by the power receiving section not to exceed aprotection voltage; and a protection voltage setting circuit configuredto set the protection voltage to a value corresponding to the feedingmethod identified by the determination circuit.
 8. The power receivingunit according to claim 1, further comprising: a protection circuithaving a plurality of overvoltage protection circuits different incircuit constant from one another, wherein the control circuit isconfigured to control the protection circuit to selectively use any oneof the plurality of overvoltage protection circuits according to thefeeding method identified by the determination circuit.
 9. The powerreceiving unit according to claim 1, further comprising: a communicationcircuit having a plurality of communication sub-circuits different incircuit constant from one another, wherein the control circuit isconfigured to control the communication circuit to selectively use anyone of the plurality of communication sub-circuits according to thefeeding method identified by the determination circuit.
 10. The powerreceiving unit according to claim 1, wherein the power receiving sectionincludes a coil and at least one capacitor.
 11. The power receiving unitaccording to claim 10, wherein the control circuit sets the targetvoltage without changing a L value of the coil.
 12. The power receivingunit according to claim 6, wherein the regulator includes a DC-DCconvertor or a low drop out.
 13. The power receiving unit according toclaim 12, wherein the low drop out allows the voltage difference to belost to generate a constant voltage.
 14. The power receiving unitaccording to claim 12, wherein the DC-DC converter has a wide variablerange of the input voltage.